> -----Original Message-----
> From: open-iscsi@googlegroups.com [mailto:open-is...@googlegroups.com]
> On Behalf Of Hannes Reinecke
> Sent: Monday, December 20, 2010 6:47 AM
> To: open-iscsi@googlegroups.com
> Cc: Rustad, Mark D
> Subject: Re: DCB support for iSCSI
> On 12/17/2010 06:55 PM, Rustad, Mark D wrote:
> > Hi all,
> >
> > I am looking into adding support for DCB into iSCSI. I think
> > it is best to do this in a way that will not require a strong
> > dependency on DCB for iSCSI. That is, installing open-iscsi
> > should not then require open-lldp to also be installed. I see
> > at least two ways to do this.
> >
> > The first is to have open-lldp supply a library that iscsid
> > can link with at run time (through dlopen/dlsym). In that way,
> > if the library is not there, iscsid can go on as usual. It
> > also allows lldpad more freedom to change over time.
> >
> > The second way is to put a little more code directly in
> > iscsid and have it interrogate lldpad for the proper priority
> > to set. If the lldpad socket isn't there, iscsid can go on as
> > usual. I am thinking that open-lldp can supply the source files
> > that would be placed directly into open-iscsi and updated as
> > needed. These source files might also be used by other network
> > applications that want to participate fully in a DCB environment.
> >
> > I had been leaning toward the first way until I started thinking
> > about iscsistart and initrds. Then it seemed that the run-time
> > linkage would create more trouble than it would be worth.
> > It started to seem like over-engineering.
> >
> I would prefer the second method.
> DCB configuration itself is quite involved and requires to
> negotiate the transfer parameter before the connection is setup.
> And as DCB is in fact quite a different beast from iSCSI we
> should keep it as a separate daemon.
> Which would also be in-line with the current fcoeadm setup.

I  would also prefer a dcb client like that allows configuring for iSCSI 
traffic.  I do need an open-lldpad as a library though but that is to integrate 
the library with libvirt to keep the architecture clean and not have libvirt 
call various exec commands to configure dcb for VMs.

> > In either case, I was thinking about adding code right before
> > the connect() call in iscsi_io_tcp_connect to set the socket
> > options based on information from lldpad. Is anything more
> > than that needed (besides doing something similar in iscsistart)?
> >
> VLAN creation.
> From what I've seen iSCSI support in DCB would work similar
> to FCoE, ie the iSCSI traffic will be sent via a separate
> VLAN. Which we would need to create, eventually.
> So basically we would need something similar to 'fipvlan'
> or integrate this functionality into open-iscsi.

Well there are more methods actually. Separating them into separate VLAN's 
would tag them to the priority of the VLAN(8 in all) however sometimes the tag 
is based on the application type port number.

So, in the iSCSI case the well known port number 3260 becomes the priority 

Usecase - Tag all iSCSI traffic to a specific port type in a virtualized 
environment. Its very cumbersome to manage vlans in the virtualized 

Also ETS determines that within the same priority group the bandwidth could be 
split further. Now, this could be per connection.  My hunch is that we need 
more flexible ways of splitting the bandwidth within a priority group per 
connection via the lldpad.

> > The socket protocol to lldpad is already versioned, so that
> > should prevent any terribly rude surprises in the future should
> > mismatched components be used together.
> >
> > Does this sound reasonable to you? Would you rather see it done
> > in a different way? Would you prefer for iscsid to simply send
> > a file descriptor to the lldpad socket and have lldpad set the
> > socket options itself?
> >
> Ugh. No. As mentioned, I fear we would need to setup a VLAN
> interface here, in which case we would be running off a
> totally different socket anyway.
> Cheers,
> Hannes
> --
> Dr. Hannes Reinecke                 zSeries & Storage
> h...@suse.de                        +49 911 74053 688
> SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
> GF: Markus Rex, HRB 16746 (AG Nürnberg)

Shyam Iyer

You received this message because you are subscribed to the Google Groups 
"open-iscsi" group.
To post to this group, send email to open-is...@googlegroups.com.
To unsubscribe from this group, send email to 
For more options, visit this group at 

Reply via email to